1. Field of the Invention
The present invention relates to a method of manufacturing a liquid crystal display panel used for a display device.
The present application claims priority of Japanese Patent Application No. 2000-85488 filed on Jun. 20, 2000, which is hereby incorporated by reference.
2. Description of the Related Art
A liquid crystal display panel has been heretofore widely used as a display device such as a TV monitor and as a display device for office automation equipment. As a method of manufacturing this liquid crystal display panel, there is known a method in which a sealing material is coated onto a periphery portion of one of a pair of transparent glass substrates, liquid crystal is dropped on this transparent glass substrate, and then the two transparent glass substrates superposed upon another are compressively attached to each other, and a method in which a pair of opposite transparent glass substrates are attached to each other with a gap therebetween, and the gap is sealed after injecting liquid crystal into the gap.
As shown in FIG. 14A and FIG. 15, as a method to drop the liquid crystal, there is a method in which spacers 102 of a thickness t, which serve to regulate a gap between the transparent glass substrates 101 and 106, are scattered on one transparent glass substrate 101, on which signal lines and scanning lines (not shown) are arranged in a matrix fashion, and a TFT and a pixel electrode (not shown) are connected to each crossing point of the signal lines and the scanning lines, and a sealing material 103 is coated onto an angular ling portion of a display area having a longitudinal dimension a and a lateral dimension b so that the sealing material 103 surrounds a peripheral portion thereof with a predetermined height h.
Next, as shown in FIG. 14B, liquid crystal 104 of a prescribed amount VL is dropped, for example, at a central portion of the display area surrounded by the sealing material 103. This prescribed amount VL is equal to a volume of a space formed between the transparent glass substrates 101 and 106 at the time when the later-described gap between the transparent glass substrates 101 and 106 becomes a prescribed value, and VL is equal to abt.
Next, as shown in FIG. 14C, the transparent glass substrate 101 mounting the liquid crystal 104 is inserted in a vacuum pressure decompression bath 105, and the other transparent glass substrate 106 in which a common electrode and a color filter (not shown) are arranged is superposed on the transparent glass substrate 101 while keeping a pressure of the vacuum decompression bath 105 at a predetermined pressure p1. At this time, residual gas 107 of a volume V1 occupies a predetermined space.
Subsequently, compressive force is gradually applied to the transparent glass substrates 101 and 106. AS shown in FIG. 14D, the transparent glass substrates 101 and 106 are pressed against each other to be compressively attached until an interval between the transparent glass substrates 101 and 106 becomes the foregoing prescribed value equal to the height t of the spacer 102. Furthermore, the pressure in the vacuum decompression bath 105 is restored to an atmospheric pressure p0, and thus the liquid crystal panel in which the liquid crystal 104 is sealed is obtained. At this time, the residual gas 107 is also compressed and visually recognized as air bubbles of a volume V2.
For example, when the prescribed amount VL of the liquid crystal 104 and the volume V1 of the residual gas 107 are calculated for a 14-inch type liquid crystal display panel, the prescribed amount VL (=abt) is 310.65 mm3 and the volume V1 (=abhxe2x88x92VL) is 1553.21 mm3, assuming a=216.1 mm, b=287.5 mm, t=0.005 mm, h=0.03 mm, and p1=1 Pa.
A volume V2 (=V1p1/p0) of the residual gas 107 after being compressed is calculated to be 0.015 mm when p0=1.013xc3x97105 Pa. If the shape of the residual gas (air bubble) 107 is assumed to be cylindrical, a cross section S (=V2/t) [mm2] of the residual gas (air bubble) 107 is 3 mm2, and a diameter f thereof is 1.9 mm.
As described above, the residual gas 107 visually recognized in the display area are sealed in the liquid crystal display panel causing a problem that a quality degradation of the liquid crystal display panel is brought about.
Therefore, for example, in Japanese Patent Laid-open No. Sho56-155920 and No. Hei03-255422, disclosed are techniques in which after a sealing material is coated onto a peripheral portion of one of a pair of transparent glass substrates, liquid crystal is dropped onto one of the transparent glass substrates so as to fill a gap between the pair of the transparent glass substrates and air bubbles are ejected from the gap. The techniques disclosed in Japanese Patent Laid-open No. Sho56-155920 and No. Hei03-255422 are hereinafter referred to as a first prior art and a second prior art respectively.
In the first prior art, as shown in FIG. 16A, after spacers (not shown) are scattered on a transparent glass substrate 201, an ultraviolet-curing sealing material 202 is coated onto a peripheral portion of the transparent glass substrate 201.
Next, as shown in FIG. 16B, a liquid crystal 203 is dropped onto the transparent glass substrate 201, and an other transparent glass substrate 204 facing the transparent glass substrate 201 is superposed thereon. At this time, a quantity of the liquid crystal 203 dropped is set larger than that necessary for displaying.
Subsequently, an ultraviolet ray is radiated onto the sealing material 202 except for a predetermined ejection portion 202H to cure the sealing material 202, and both of the transparent glass substrates 201 and 204 are pressed from both sides thereof. The liquid crystal 203 fills a gap between both of the transparent glass substrates 201 and 204. A surplus amount of the liquid crystal 203 is ejected through the ejection portion 202H outside the sealing material 202. Simultaneously, air bubbles are also exhausted.
Then, as shown in FIG. 16C, an ultraviolet ray is irradiated onto the ejection portion 202H of the sealing material 202 to cure it, thus sealing the liquid crystal 203 between the transparent glass substrates 201 and 204.
In the second prior art, as shown in FIG. 17A, after spacers (not shown) are scattered on a transparent glass substrate 301, a sealing material 302 is coated on a peripheral portion of the transparent glass substrate 301. At this time, an opening portion 302H is provided in a part of a coating pattern of the sealing material 302.
Next, as shown in FIG. 17B, a liquid crystal 303 is dropped on the transparent glass substrate 301, and an other transparent glass substrate 304 facing the transparent glass substrate 301 is superposed thereon. At this time, a quantity of the dropped liquid crystal 303 is set larger than that necessary for displaying.
Both of the transparent glass substrates 301 and 304 are pressed from both sides thereof, and the liquid crystal 303 fills a gap between the transparent glass substrates 301 and 304. Then, a surplus amount of the liquid crystal 303 is ejected from the opening portion 302H. At this time, air bubbles are simultaneously exhausted.
Then, as shown in FIG. 17C, the sealing material 302 is cured, and the opening portion 302H is sealed by an adhesive 305.
However, in the foregoing first and second prior arts, there is a problem that the surplus amounts of the liquid crystal 203 and 303 are needed and expensive liquid crystal material is wasted.
Furthermore, in the first prior art, since the surplus amount of the liquid crystal 203 is exhausted to the outside over the sealing material 202, there is a problem that the sealing material 202 is also swept away together with the liquid crystal 203 in exhausting the liquid crystal 203, thus lowering adhesion. Moreover, there is a problem that a contaminant is mixed in the liquid crystal 203 from the outside through the flowing-out portion in the sealing material 202, and gas flows into the liquid crystal 203, thus degrading quality of the liquid crystal display panel.
In the second prior art, since a step for sealing the opening portion 302H is inevitable in addition to a step for curing the sealing material 302, there is a problem that it the manufacturing steps of the liquid crystal display panel take a lot of troubles and an increase in cost is brought about.
In view of the above, it is an object of the present invention to provide a method of manufacturing a liquid crystal display panel capable of manufacturing a high quality liquid crystal display panel without wasting liquid crystal and without making manufacturing steps troublesome.
According to a first aspect of the present invention, there is provided a method of manufacturing a liquid crystal display panel in which liquid crystal is held between a pair of panel substrates facing each other, on which an electrode is formed, includes: a step for coating a sealing material on a plane of at least one of the panel substrates, on which the electrode is formed, with a predetermined coating pattern having a notch portion; a step for dropping the liquid crystal on the plane of at least one of the panel substrates, on which the electrode is formed, with a predetermined dropping pattern; a step for superposing both of the panel substrates upon another while sandwiching the sealing material and the liquid crystal between both of the panel substrates; and a step for pressing both of the panel substrates against each other, wherein in the sealing material coating step, a notch width of the notching portion is set to a value so that the notch portion is blocked after the both of the panel substrates are pressed against each other in the substrate pressing step.
In the foregoing first aspect, a preferable mode is one wherein in the sealing material coating step, the notch width of the notch portion is set so that the notch portion is blocked before the liquid crystal reaches the notch portion after starting to press both of the panel substrates in the substrate pressing step.
Also, a preferable mode is one wherein in the sealing material coating step, the notch width of the notch portion is set to be equal to an increased amount of a width of the sealing material or less, which is obtained by subtracting a width of the sealing material when the sealing material is coated in the sealing material coating step from a width of the sealing material after both of the panel substrates are pressed against each other in the substrate pressing step.
Also, a preferable mode is one wherein in the sealing material coating step, a plurality of notch portions are provided, and of two notch portions selected arbitrarily from the plurality of notch portions, a notch width of one notch portion which the liquid crystal reaches earlier than the other notch portion in the substrate pressing step is set to be smaller than that of the other notch portion which the liquid crystal reaches later.
Also, a preferable mode is one wherein in the sealing material coating step, the notch width of the notch portion is set to approximately 0.75 times the increased amount of the width of the sealing material.
Also, a preferable mode is one wherein a quantity of the liquid crystal dropped in the liquid crystal dropping step is set to be equal to a volume of a layer-shaped space or less, which is formed by both of the panel substrates and the sealing material immediately after both of the panel substrates are superposed in the substrate pressing step.
Also, a preferable mode is one wherein the quantity of the liquid crystal dropped in the liquid crystal dropping step is set to be approximately equal to a volume of the layer-shaped space formed by both of the panel substrates and the sealing material after both of the panel substrates are pressed against each other in the substrate pressing step.
Also, a preferable mode is one wherein in the substrate pressing step, by pressing both of the panel substrates against each other, both of the panel substrates are compressively attached to each other, the liquid crystal is allowed to fill the layer-shaped space, residual gas is exhausted from the layer-shaped space through the notch portion, and the notch portion provided in the sealing material coating step is blocked.
Also, a preferable mode is one wherein in the liquid crystal dropping step, the predetermined dropping pattern is adopted based on at least dimensions of the display area used for displaying, which is the plane of the panel substrate where the electrode is formed.
Also, a preferable mode is one wherein in the sealing material coating step, the predetermined coating pattern is adopted based on at least dimensions of the display area used for displaying, which is the plane of the panel substrate where the electrode is formed.
Also, a preferable mode is one wherein in the sealing material coating step, the sealing material is coated so as to show approximately an angular ring appearance with predetermined width and height.
Also, a preferable mode is one wherein in the sealing material coating step, the sealing material is coated so that the notch portion is formed at least in a corner of the display area, and in the liquid crystal dropping step, the liquid crystal is dropped on a central portion of the display area.
Also, a preferable mode is one wherein the dropping pattern of the liquid crystal is set based on an aspect ratio of the display area.
According to a second aspect of the present invention, there is provided a method of manufacturing a liquid crystal display panel in which liquid crystal is held between a pair of panel substrates facing each other, on which an electrode is formed, includes: a step for coating a sealing material on a plane of at least one of the panel substrates, on which the electrode is formed, with a predetermined coating pattern having a notch portion; a step for dropping the liquid crystal on the plane of at least one of the panel substrate on which the electrode is formed, with a predetermined dropping pattern; a step for superposing both of the panel substrates upon another while sandwiching the sealing material and the liquid crystal between both of the panel substrates; and a step for pressing both of the panel substrates against each other, wherein in the sealing material coating step, the sealing material surrounding a display area and a comparatively small non-display area is coated outside the display area used for displaying, which is the plane of the panel substrate where the electrode is formed, so that the small non-display area which continues to the display area is formed and a notch portion is formed on the outer periphery of the small non-display area, and in the substrate pressing step, an air bubble accommodation portion for accommodating residual gas is formed in the small non-display area after the panel substrates are superposed upon another.
Also, a preferable mode is one wherein a notch width of the notch portion is set so that the notch portion is blocked after both of the panel substrates are pressed against each other in the substrate pressing step.
Also, a preferable mode is one wherein the notch width of the notch portion is set so that the notch portion is blocked before the liquid crystal reaches the notch portion after starting to press both of the panel substrates in the substrate pressing step.
Also, a preferable mode is one wherein the notch width of the notch portion is set to be equal to an increased amount of a width of the sealing material or less, which is obtained by subtracting a width of the sealing material when the sealing material is coated in the sealing material coating step from a width of the sealing material after both of the panel substrates are pressed against each other in the substrate pressing step, and a notch width of the notch portion provided outside the small non-display area is set to a value smaller than a width of an opening between the display area and the small non-display area.
Also, a preferable mode is one wherein in the substrate pressing step, by pressing both of the panel substrates against each other, both of the panel substrates are compressively attached to each other, the liquid crystal is allowed to fill a layer-shaped space corresponding to the display area, the layer-shaped space being formed by both of the panel substrates and the sealing material, residual gas is exhausted from the layer-shaped space through the notch portion, and the notch portion provided in the sealing material coating step is blocked in a state where the residual gas is partially accommodated in the air bubble accommodation space.
With the above configurations, in the sealing material coating step, the notch widths of the notch portions are set so that the notch portions are blocked after both panel substrates are pressed against each other in the substrate pressing step. Therefore, the pressing of the panel substrates against each other, filling of the liquid crystal, the exhaustion of the residual gas, and sealing of the notch portion can be performed approximately at the same time in the same step. The present invention can contribute to shortening of manufacturing time and cost reduction without complicating manufacturing steps by providing a new step such as a sealing step.
The notch width of the notch portion is set in the sealing material coating step so that the notch portion is blocked before the liquid crystal reaches the notch portion in the substrate pressing step. Therefore, wasteful outflow of the liquid crystal can be prevented.
In addition, since the residual gas is exhausted through the notch portion while spreading the liquid crystal, degradation of quality of the liquid crystal panel due to the residual gas can be prevented, and the liquid crystal display panel of high quality can be manufactured.
The notch width of the notch portion is set to the increased amount of the width of the sealing material or less, whereby the notch portion is surely blocked, and hence the leakage of the liquid crystal can be surely prevented. Accordingly, the present invention can provide the method of manufacturing a liquid crystal display panel of high reliability.
The amount of the liquid crystal dropped in the liquid crystal dropping step is set to a volume approximately equal to the volume of the layer-shaped space formed by the panel substrates and the sealing material after the panel substrates are pressed against each other in the substrate pressing step, whereby the liquid crystal display panel can be manufactured by use of the liquid crystal material of an adequate amount without wasting the liquid crystal material.
Furthermore, the residual gas can be exhausted surely and effectively by determining the dropping pattern of the liquid crystal based on at least the dimensions of the display area.
Furthermore, the residual gas can be exhausted surely and effectively by determining the coating pattern of the sealing material based on at least the dimensions of the display area.
Still furthermore, the air bubble accommodation space is formed outside the display area, and the residual gas is collected in the air bubble accommodation space, whereby a quality of the liquid crystal display panel can be further enhanced.